Craft brewing revolves around one main goal; to always create the best-tasting beers. Because of that, craft brewers spend a lot of time selecting the best available ingredients, and optimizing their brewery in such way to create the best possible taste. This sometimes goes at the expense of time, costs, and efficiency. In this article we will look at the causes of low efficiency in the brewhouse, and how to take steps to prevent them.
Why should you care? Isn’t craft brewing all about being creative and artistic? It is, yet at the same time you also want to make some money. Making a few small adjustments could save you a lot of money in the long run. Improving from 75% to 85% on a 1000liter system could save you 1 bag of malts per brew. Moreover, the efficiency in the brewhouse will lead to energy and water savings in the brewhouse and boiler. Being inefficient is not the same as being crafty!
Let’s start by defining brewhouse efficiency. This indicates how much of the potential fermentables made it into a wort, with the measured gravity and the target volume. Sometimes this is also called the efficiency into the boiler. These two should not be confused with efficiency into fermenter as this number also takes hop absorption and transferring losses into consideration. In the end it doesn’t really matter which definition you use, as long as you measure it consistently to compare previous results and relate it to the same measurement when comparing with other brewers.
Determining the brewhouse efficiency
Most craft brewers nowadays use a brewing software (Beersmith, ProMash, Brewersfriend, etc.) to calculate different efficiencies at different stages of the process. Yet to understand what the numbers mean, we must understand the formula behind it.
- Brewhouse efficiency = actual grain extract / potential grain extract
- Actual grain extract = wort volume in l * specific gravity in sg * Plato / 100
- Potential grain extract = weight of grist in kg * fine grind extract %
The formula for the actual grain extract multiplies the volume in liters with the specific gravity of the wort, which gives the weight of the wort. That is then multiplied by the wort strength expressed in Plato which expresses how much of that wort weight comes from extract (sugars, proteins, etc.). Make sure all volume measurements are corrected for differences in temperature, as volume increases when temperature does.
The potential grain extract is the weight of the extract that can theoretically be extracted from the grist. This number is easy because it can be found on the actual malt analysis of your batch.
Note that the extract content is usually given as a percentage of the dry malt weight, but that as it is stored with a moisture content (MC) of 3-5%. This should be taken into account when determining the actual extract content in the malt (100% – MC)/100%.
There are many factors that can influence this calculation. The reliability of the outcome is linked to the reliability of the output. Possible error factors are incorrect reading of gravity, volume or weight measurements. For example: if the grain weight has an error of 5% (which is 10kg for a 200kg grist), the calculated efficiency will also have a 5% error. A calculated efficiency of 70% could actually be between 66% and 74%.
The following measurement errors can be seen as reasonable:
- 1% error for the grain weight (0.1kg on 10kg).
- 2% error for the specific gravity or wort strength (0.25 on 12P).
- 2% error on the volume measurement. This means (10l on 500l).
- Combined the efficiency can be calculated with 5% accuracy.
How good is my efficiency?
Now that we know our efficiency, we can compare it and evaluate how good it is. A lot of opinions exist on what efficiency numbers are good and which ones are bad. In the end, it depends on a lot of factors. The following table lists a range of brewhouse efficiencies that can be expected from various brewing systems. Note that these are efficiencies measured in the boil kettle and not in the fermenter.
| Brewing system | Typical brewhouse efficiency range |
| Large-scale commercial brewing | 92% – 100% |
| Fly sparging | 80% – 95% |
| Batch sparging | 75% – 90% |
| No sparge | 65% – 80% |
How to improve your brewhouse efficiency?
This is the part where it becomes interesting. There are 3 main processes that affect the brewhouse efficiency: milling, mashing and lautering. Besides these processes the quality of ingredients that you use also play a significant role. Let’s discuss them one by one.
1. Quality malt
Superior quality malt helps to increase efficiency. High quality malt is produced from European 2-row spring barley. The barley is carefully selected on size and consists of at least 95% kernels larger than >2.5mm. This consistent and large size ensures better milling and a better ratio of starches vs. husk content.
The extract level in itself is of course a quality aspect, but not direct related to your efficiency. Meaning, you can have a very good efficiency of a low quality and low extract malt by getting everything out. What does affect the efficiency is the differential between the fine grind and coarse grind extract level. This difference should be less than 1%, whereas in some instances this is 3% or more. This 3% you can immediately subtract from your efficiency, as in real life you will not use the fine grind method.
A third quality aspect influencing friability is the measure of a malt’s readiness to crumble when subjected to crushing or milling. A high friability level malt is easier to mill also tells you something about the modification. A fourth quality aspect is the diastatic power of the malt. The higher that power is, the more enzymes are in the mash and the more starch can be converted. Too much enzymatic power is a problem for all-malt brewers. It can be difficult to control and can have inconsistent outcomes, and negatively influences the ‘maltiness’ of the beer.
Another aspect to consider is the protein level. A high protein level makes modification more difficult. It might be more difficult to lauter as it can create a dense layer of precipitated protein on top of the grain bed.
2. Milling
When you are using good quality malts, and still suffer low efficiencies, it might be good to have a look at your milling. A lot of efficiency gains can be made here. Inspect your milling regularly. Are there any uncrushed kernels? Are there any kernels that are cracked, but the endosperm doesn’t come out easily?
A good milling produces little flour, but fully separates the inner meal of the kernel from the husk. A common mistake is to mill too fine, producing lots of flour and broken husks. This will produce a very tight filter bed that might be difficult to lauter and/or channel. If you have problems with low efficiencies and find lots of flour in your millings, try out a coarser grind. Unopened kernels or pieces that are too large can be signs of a too coarse grind, low friability or under-modified malt. They reduce efficiency as well. As a result, a compromise needs to be made between a crush that is tight enough for sufficient conversion efficiency, yet coarse enough for easy lautering.
3. Mash parameters
Temperatures between ~63ºC and 80ºC are known to fully convert a mash. The exact temperature that should be chosen for the saccharification rest depends on the mash schedule, rest time, attenuation target and diastatic power of the malt. The different temperatures do not really influence the efficiency, so use these temperatures to influence the flavour of your final beer, not your efficiency.
The enzymes – that are responsible for starch conversion – are not only sensitive to temperature, but they are also sensitive to pH. Brewing literature shows that the mash pH should be between 5.5 and 5.6 (measured at room temperature) for optimal conversion efficiency. In some studies, a 2% decrease in brewhouse efficiency was found when pH was at least .2 out of range.
4. Lauter efficiencies
The goal of lautering is to recover as much extract from the malt grist as possible. The speed and efficiency of the lautering greatly depends on the grain bed. A higher volume of unbroken husks will increase your lautering speed. Another way to keep your grain bed loose is to keep the stirring during the mash to a minimum, and to not mill your grains too fine. Slow down the initial lauter speed, and gradually increase it to prevent channeling.
Another factor for the achievable efficiency, aside from the lauter method, is the amount of grain and the pre-boil volume. The larger the grist in relation to the batch size, the more wort gets trapped in that grist after running off. As a result larger beers generally show lower brewhouse efficiency. If more water is used for sparging, more of the extract can be washed out of the grain. The result is higher brewhouse efficiency but also a higher pre-boil volume which requires longer or more intensive boiling which costs a lot of energy. That and the increased sparging can be detrimental to the beer quality and should not be used to fix an efficiency problem.
While a low efficiency can be an indication of a suboptimal mashing and lautering process, very high efficiency does not necessarily mean the best beer possible. Therefore it is important to find a balance between the quality of your beer, the efficiency of your brewhouse and the energy consumed.